I am about to order select S11 for my ultrasonic.
A friend of mine tells me that select fins should be 2 cm smaller/shorter than deboichet.
An example: I want a new fin for my ultrasonic and overdrive 9.5; should I buy select S11: What size?
Recommended by remi is deboichet 58. But select S11?

The new Drake Race is looking good, and costs less than the Deb. If you go Select S11, then I would recommend going with a 55cm as the S11 is super powerful. If you want a bit extra control and speed, go for S10 57cm. S11 for super light wind for strong back legs or S10 to make board feel easier. Size for size, S10 is faster c/w S11